Module mod_auth

Summary

This module allows the use of HTTP Basic Authentication to
restrict access by looking up users in plain text password and
group files. Similar functionality and greater scalability is
provided by mod_auth_dbm and mod_auth_db. HTTP Digest
Authentication is provided by mod_auth_digest.

Note that these credential-based security mechanisms are
only as strong as your Web server's security. As a rule, they
are not as strong as the operating system's own security
system.

Directives

The mod_auth module supports the following
keywords that can be given to the Require directive:

user username [...]

The supplied username and password must be in the AuthUserFile database, and the
username must also be one of those listed on the Require
directive.

group groupname [...]

The supplied username and password must be in the AuthUserFile database, and the
username must also be a member of one of the named groups in
the AuthGroupFile database.

valid-user

The supplied username and password must be in the AuthUserFile database. Any valid
username from that file will be allowed.

file-owner

[Available after Apache 1.3.20] The supplied username and
password must be in the AuthUserFile database, and the
username must also match the system's name for the owner of
the file being requested. That is, if the operating system
say the requested file is owned by jones, then
the username used to access it through the Web must be
jones as well.

file-group

[Available after Apache 1.3.20] The supplied username and
password must be in the AuthUserFile database, the name of
the group that owns the file must be in the AuthGroupFile database, and the
username must be a member of that group. For example, if the
operating system says the requested file is owned by group
accounts, the group accounts must
be in the AuthGroupFile database and the username used in the
request must be a member of that group.

Consider a multi-user system running the Apache Web server,
with each user having his or her own files in
~/public_html/private. Assuming that there is a
single AuthUserFile database that lists all of their usernames,
and that their Web usernames match the ones that actually own
the files on the server, then the following stanza would allow
only the user himself access to his own files. User
jones would not be allowed to access files in
/home/smith/public_html/private unless they were
owned by jones instead of smith.

The AuthGroupFile directive sets the name of a textual file
containing the list of user groups for user authentication.
File-path is the path to the group file. If it is not
absolute (i.e., if it doesn't begin with a slash), it
is treated as relative to the ServerRoot.

Each line of the group file contains a groupname followed by
a colon, followed by the member usernames separated by spaces.
Example:

mygroup: bob joe anne

Note that searching large text files is very
inefficient; AuthDBMGroupFile
should be used instead.

Security: make sure that the AuthGroupFile is stored outside
the document tree of the web-server; do not put it in
the directory that it protects. Otherwise, clients will be able
to download the AuthGroupFile.

The AuthUserFile directive sets the name of a textual file
containing the list of users and passwords for user
authentication. File-path is the path to the user
file. If it is not absolute (i.e., if it doesn't begin
with a slash), it is treated as relative to the ServerRoot.

Each line of the user file contains a username followed by a
colon, followed by the crypt() encrypted password.
The behavior of multiple occurrences of the same user is
undefined.

The utility htpasswd
which is installed as part of the binary distribution, or which
can be found in src/support, is used to maintain
this password file. See the man page for more
details. In short

htpasswd -c Filename username
Create a password file 'Filename' with 'username' as the
initial ID. It will prompt for the password. htpasswd
Filename username2
Adds or modifies in password file 'Filename' the 'username'.

Note that searching large text files is very
inefficient; AuthDBMUserFile
should be used instead.

Security:

Make sure that the AuthUserFile is stored outside the
document tree of the web-server; do not put it in
the directory that it protects. Otherwise, clients may be
able to download the AuthUserFile.

Also be aware that null usernames are permitted, and null
passwords as well (through Apache 1.3.20). If your
AuthUserFile includes a line containing only a colon (':'), a
'Require valid-user' will allow access if both
the username and password in the credentials are
omitted.

Setting the AuthAuthoritative directive explicitly to
'off' allows for both authentication and
authorization to be passed on to lower level modules (as
defined in the Configuration and
modules.c files) if there is no
userID or rule matching the supplied
userID. If there is a userID and/or rule specified; the usual
password and access checks will be applied and a failure will
give an Authorization Required reply.

So if a userID appears in the database of more than one
module; or if a valid Require directive applies to
more than one module; then the first module will verify the
credentials; and no access is passed on; regardless of the
AuthAuthoritative setting.

A common use for this is in conjunction with one of the
database modules; such as mod_auth_db.c, mod_auth_dbm.c,
mod_auth_msql.c, and mod_auth_anon.c.
These modules supply the bulk of the user credential checking;
but a few (administrator) related accesses fall through to a
lower level with a well protected AuthUserFile.

Default: By default; control is
not passed on; and an unknown userID or rule will result in an
Authorization Required reply. Not setting it thus keeps the
system secure; and forces an NCSA compliant behavior.

Security: Do consider the implications of allowing a user to
allow fall-through in his .htaccess file; and verify that this
is really what you want; Generally it is easier to just secure
a single .htpasswd file, than it is to secure a database such
as mSQL. Make sure that the AuthUserFile is stored outside the
document tree of the web-server; do not put it in the
directory that it protects. Otherwise, clients will be able to
download the AuthUserFile.